1. Field of the Invention
The invention relates to the field of synthesizing digital waveforms having transitions at arbitrary points in time, particularly for metal oxide semiconductor (MOS) circuits.
2. Art Background
It is quite common for intergrated circuits to perform many functions, such as addition and subtraction, that hitherto have been performed by analog techniques. However, many furnction in computing are still performed with analog techniques. Examples of such functions are frequency multiplication, random waveform synthesis, duty-cycle conversion and phase shifting. Some of these functions are performed individually by dedicated circuits but others are not possible at all using existing analog techniques or digital circuitry.
Generally, in the prior art, two methods exist for frequency multiplication: using a phase-locked loop (PLL) or dividing a high frequency reference clock down to the desired multiply frequency. Although the prior art methods accomplish frequency multiplications by an integer, the PLL method is difficult of implement in MOS technology, while the frequency-division method does not generally provide an output that is entirely synchronized to the input. Furthermore, no general applicable methods are known for performing duty-cycle conversion nor any generally applicable methods are known for performing random waveform generation or controlling phase shifit.
As will be shown below, the present invention provides a circuit for synthesizing digital waveforms having transitions at arbitrary points in time. Using CMOS circuits, the present invention performs a variety of functions such as frequency multiplication by an integer, frequency multiplication by a rational number, random waveform synthesis, duty-cycle conversion and phase shifting.